I use a rubber broom (see link below) to help push/tuck in the canvas as much as possible. You want to get the vinyl/canvas as flat as you can, which will help.
In my case I can't leave any bedding or my mattress topper on, as it's impossible to latch else.
I pull all my privacy curtains to the middle of the rail, as there seems to be a lot going on in the corners, so I try to reduce the bulking as much as possible.
Once it is down, we leave it for 15 minutes, to let gravity do the rest. We finish packing the truck, deal with the trash, toilet break. So latching is the last thing we do.
Also, don't be afraid to adjust your latches accordingly on each trip. Normally, going to the camp trip mine are adjusted pretty snug, as the pop-up has sat in the garage a couple of weeks, but I will slack them off a bit coming home, as the canvas/vinyl hasn't settled enough for a tight latch.
I have to admit closing up and tucking in is one of things, that could drive me to the dark side! (hard side trailer) It's always a pain and honestly, no two pack away/tuck ins are ever the same! sometimes it lays nice & flat, sometimes it doesn't. So you are not alone!
https://www.amazon.com/dp/B000EFDOOA...r%2Bbroom&th=1